1. Field of the Invention
The invention relates to third generation (3G) terminal communication, and in particular, to a communication method supporting various versions of physical layer modules.
2. Description of the Related Art
Mobile voice and digital communication requirements are increasing in complexity, rendering insufficient transfer rate and bandwidth for current communication systems. A third generation (3G) mobile communication standard provides higher bandwidth utilization and transfer rate. Various 3G systems have been proposed, with a universal mobile transmission system (UMTS) from Europe the most widely adopted standard.
FIG. 1 shows a conventional UMTS architecture, in which three layers are provided to process communication data. A physical layer 114 is implemented by hardware, modulating data with carrier frequency into radio signals for transmission. A second layer is implemented by software, comprising a radio link control (RLC) 110 and a media access control (MAC) 112. The MAC 112 multiplexes transmission data based on commands received from the radio resource control (RRC) 104, mapping packets received over various logical channels 270 from the RLC 110 to corresponding transport channels 280 according to the priority thereof. The MAC 112 also supports wireless resource domination including priority, client identification and throughput measurement.
RLC 110 manages transmission quality control for the UMTS. Packets are divided, transmitted, retransmitted, and combined by the RLC 110 based on corresponding quality level requirements. Four quality levels are defined according to the UMTS, including “conversational”, “streaming”, “interactive” and “background”. The RLC 110 performs flow control, packet reordering, packet encryption and error detection to accomplish the pack division and transmission.
The first layer protocol comprises at least three software implemented logic blocks, radio resource control (RRC) 104, Broadcast/Multicast Control (BMC) 106 and packet data convergence protocol (PDCP) 108. The UMTS provides the PDCP 108 to enhance packet transfer efficiency by compressing packet headers. For example, a voice over IP (VOIP) packet header comprises 40 to 60 bytes, and the data payload comprises only 20 bytes. The header is thus compressed by the PDCP 108 to enhance transfer efficiency. The BMC 106 handles broadcast signals transmitted from the base station, such as message storage and display. The RRC 104 is the kernel of the UMTS, handling wireless resource message exchange, wireless resource configuration, quality control, channel format configuration, packet division and combination control, and non-access stratum (NAS) protocol.
The UMTS in FIG. 1 also comprises a NAS 102 handling user interface protocols. The NAS 102 comprises connection management, mobility management and radio access bearer management (RABM) 204. The NAS in UMTS is inherited from GSM phase 2+. In 3G systems, the NAS 102 is implemented in the mobile terminal and MSC/SGSN stations. The RABM 204 provides configuration and management of the logic channels for packet transmission. The UMTS supports pack transmission of transfer rate and quality, and the logic channels are built, adjusted, maintained, and released by the RABM 204 based on control of the NAS.
During voice communication, an adaptive multi-rate codec (AMR) codec 210 generates control signal 250 (control plane) and data signal 260 (user plane) bound for the remote, and the first, second and third layers convert the control signal 250 and data signal 260 to radio signals for transmission. The RRC 104 individually commands the BMC 106, the PDCP 108, the RLC 110, the MAC 112 and physical layer 114 to build logical channels corresponding to the control signal 250 and data signal 260.
According to the standard, a plurality of logical channels 270 link the RLC 110 and MAC 112, and a plurality of transport channels 280 link the MAC 112 and physical layer 114. The RLC 110 sends various command signals to the MAC 112 via logical channels 270 comprising BCCH, PCCH, CCCH and DDCH. The command signals are then diverted to the physical layer 114 via the transport channels 280. The mapping between the logical channels 270 and transport channels 280 may be one-to-many. The physical layer 114 transmits radio signals after a modulation operation. The physical layer 114 is typically an external module provided by various hardware vendors with protocols thereof differing. For example, if the second layer is implemented by software, consuming significant system resources in processing the data signal 260, the physical layer 114 may be designed to directly receive data signal 260 from the codec 210 without occupation of the second layer. An improved UMTS architecture is desirable to provide compatibility with various specifically designed physical layers 114 in one module.